Real-Time Scheduling of Tertiary Storage

* 1 mei, 16.45 uur

promotie Maria Lijding, faculteit Informatica: ‘Real-Time Scheduling of Tertiary Storage’

Today multimedia data are generally stored in secondary storage (hard disks) and delivered to the users from there. However, the amount of storage capacity needed for a multimedia archive is large and constantly growing with the expectations of the users. Tertiary-storage jukeboxes can provide the required storage capacity in an attractive way if the data can be accessed with real-time guarantees. The main challenges to make this happen are the high media-switching times in a jukebox and the potential for resource-contention resulting from its shared resources.

Our hierarchical multimedia archive (HMA) provides flexible real-time access to data stored in tertiary storage. The HMA can serve complex requests for the real-time delivery of any combination of media files it stores. Such requests can result, for instance, from playing a playlist of music and video clips, or from a database query to compile the historical background for a news program.

The efficient heuristic jukebox scheduler Promote-IT is the key component of the HMA that guarantees the in-time promotion of data from tertiary to secondary storage, which is used as buffer and cache. Promote-IT provides short response and confirmation times and makes good use of the jukebox resources. It separates scheduling and dispatching and effectively uses this separation to dispatch tasks earlier than scheduled, if the resource constraints can be respected and no task misses its deadline. Formally, Promote-IT is based on a scheduling problem modeled as a flexible flow shop with three stages (load, read, unload). It can deal with a wide variety of requests and types of jukebox hardware.


prof. dr. Sape Mullender


drs. B. Meijering, telefoon (053) 489 43 85